A vehicle is typically equipped with at least one device for generating a sound that is audible in the vehicle occupant compartment. The sound is provided as a signal for alerting a vehicle occupant to a vehicle condition such as an open door or an unfastened seat belt.
The sound generating device is contained in a housing which may also contain other electrically actuatable signaling devices. An assembled unit of those parts, including the housing and the devices contained in the housing, must withstand environmental conditions of temperature and humidity when installed in a vehicle. In accordance with this requirement, a production run of assembled units is evaluated by testing a group of sample units. The group of sample units is exposed to specified conditions of temperature and humidity in an environmental simulation chamber. The sample units must also undergo acoustic testing of the sound generating devices contained in the housings. Since each sound generating device must then be distinguished acoustically from the others, the sample units must be acoustically tested individually rather than in a group.